It is well known that before being stored, a large part of currently produced forage is compacted and packaged in the form of substantially cylindrical or prismatic bales. To prevent fermentation which would alter the forage during its storage, before being stored the bales may be subjected to artificial drying by appropriate apparatus.
Known artificial drying plants comprise substantially a ventilation chamber provided with air blowing apertures, at each of these apertures there being positioned one or two opposing flat faces of a bale to be dried. A dry air stream is conveyed through the blowing apertures to pass through the forage mass, so drying it. This dry air stream is produced by a centrifugal blower connected to the ventilation chamber.
The main drawback of these drying plants is irregular dry air distribution within the bale mass. This produces non-uniform drying of the forage due to air loss caused by preferential passages in the air flow which arise within the bale because of its lack of uniformity, with consequent considerable energy wastage and a lengthening of the drying time.
This phenomenon is even more apparent in soft-core bales, as the presence of more compacted peripheral forage regions means that the flow of drying air is greater along the bale axis and through its lower side surface. A critical region is therefore created, located in the bale upper region, which requires more time for drying.
Various solutions have been proposed for obviating this problem, such as using a dry air outlet aperture of ring shape instead of circular, or hindering air exit from the top of the bale by a sort of cover. The proposed solutions have not however given satisfactory results. In this respect, the bale drying is still non-uniform with consequent risk of fermentation in the case of bales of relatively high average moisture content (for example exceeding 40%). In addition, to reduce the risk of obtaining a fermentation region to a minimum, the drying action of the entire bale is often protracted, with considerable energy wastage. A further drawback is the fact that significant quantities of dry air can escape between the blowing aperture and the bale surface, with further energy wastage.
Another known system is to stack two bales of moist forage by sandwiching them between two air blowing chambers and blow air through circular blowing apertures. This solution has also not given good results, being of limited efficiency because of the excessive weight acting on the lower end of the underlying bale.
A further known system (see EP-A-0534382) is to use manifolds or headers between one bale and another provided with blowing apertures bordered by projecting peripheral rings which are inserted into the bale and achieve a certain seal. However these headers are not self-supporting and are fed by dead channels. This has substantially improved the effectiveness of the apparatus in that each blowing aperture is assigned to drying, and in fact dries, only its relative half of a bale. However the efficiency is still too penalized with regard to the lower bales, because these latter are squashed by the weight of the bales stacked on them, and because of preferential dry air paths which arise in the bale because of the kinetic energy which the air originating from the channels possesses.